Dielectric porcelain composition and high frequency device using the same

ABSTRACT

A dielectric porcelain composition of the present invention includes a first component and second component. If the first component is represented by the general formula of xBaO—yNd 2 O 3 -zTiO 2 -wBi 2 O 3  (provided that x+y+z+w=100), x, y, z, and w satisfy 12≦x≦16, 12≦y≦16, 65≦z≦69, and 2≦w≦5, respectively. The second component includes 30 to 37 wt % of BaO, 33 to 46 wt % of SiO 2 , 8 to 12 wt % of La 2 O 3 , 3 to 7 wt % of Al 2 O 3 , 0 to 1 wt % of SrO, 0 to 10 wt % of Li 2 O, 0 to 20 wt % of ZnO, and 7 wt % or less of B 2 0 3 . The compounding ratio of the second component is between 10 wt % and 30 wt % when the sum of the first and second components is 100. In addition, 0.1 to 1 parts by weight of Li 2 O and 3 to 10 parts by weight of ZnO, relative to 100 parts by weight of the sum of the first and second components, is also contained as a third component. An average particle diameter of the dielectric mixed powder forming dielectric porcelain composition before firing is 0.9 μm or less.

TECHNICAL FIELD

The present invention relates to dielectric porcelain compositions andhigh frequency devices using the same.

BACKGROUND ART

There is growing demand for equipment to be downsized in line with thedevelopment of mobile phones and wireless LAN communications that employthe microwave bands in the electromagnetic spectrum. To downsizeterminal equipment, it is necessary to downsize the high frequencydevices it employs, such as high frequency filters and resonators.

These high frequency devices are configured with a capacitor and aninternal electrode forming a strip line disposed as required in an innerlayer of a laminated body composed of dielectric porcelain. The size ofa high frequency device using the same resonance mode is in inverseproportion to the square root of the relative permittivity (εr) of thedielectric material employed. Accordingly, to manufacture a smallresonance device, a material with a relatively high relativepermittivity is needed. However, the relative permittivity needed variesaccording to the frequency band used. With equipment adopting everhigher frequencies, though, the demand for high relative permittivitymaterials is reducing.

Another characteristic required for the dielectric material used fordielectric porcelain is low loss in the high frequency range. In otherwords, a high Q value or low frequency-temperature characteristic (TCF)is needed. The Q value is inversely related to dielectric loss (tan δ).

On the other hand, attempts are being made to downsize high frequencydevices with high performance by adopting a laminated structure ofconductor and dielectric porcelain composition. When a conductor is usedin a high frequency range, such as the microwave bands, highconductivity is required. Accordingly, Ag, Cu, or their alloys aretypically used as an internal electrode. To achieve the laminatedstructure of conductor and dielectric porcelain composition as describedabove, it is necessary to simultaneously fire the internal electrode anddielectric porcelain composition. A material which can be denselysintered under firing conditions that avoid dissolution and oxidizationof a conductive metal forming the internal electrode is thus needed.More specifically, the dielectric porcelain composition needs to besintered at a temperature lower than the melting point of the conductivemetal used. If Ag is used, the material needs to be sintered at atemperature lower than the melting point of Ag (961° C.). U.S. Pat. No.5,273,944 proposes a material of the Bi₂O₃—CaO—Nb₂O₅ as one example ofthis type of microwave dielectric porcelain.

However, although conventional Bi₂O₃—CaO—Nb₂O₅ porcelain can be sinteredat a low temperature of 900° C., allowing firing together with Ag, itsmechanical strength is relatively low, which is 140 MPa. Accordingly,when a laminated element is formed, a drop impact test reveals, inparticular, that cracking is likely to occur from the terminalelectrodes of the laminated element mounted on a printed circuit board.

SUMMARY OF THE INVENTION

A dielectric porcelain composition of the present invention includes afirst component and second component. If the first component isrepresented by the general formula of xBaO—yNd₂O₃-zTiO₂-wBi₂O₃; x, y, z,and w satisfy 12≦x≦16, 12≦y≦16, 65≦z≦69, and 2≦w≦5, provided that x, y,z, and w are molar ratios and x+y+z+w=100. The second component is acomposition of BaO (30 to 37 wt %), SiO₂ (33 to 46 wt %), La₂O₃ (8 to 12wt %), Al₂O₃ (3 to 7 wt %), SrO (0 to 1 wt %), Li₂O (0 to 10 wt %), ZnO(0 to 20 wt %), and B₂O₃ (7 wt % or less). A compounding ratio of thesecond component is between 10 wt % and 30 wt % when the sum of thefirst and second components is 100. In addition, 0.1 to 1 wt % of Li₂Oand 3 to 10 wt % of ZnO, relative to 100 wt % of the sum of the firstand second components, is also contained as the third component. Theaverage particle diameter of the dielectric mixed powder formingdielectric porcelain composition before firing is 0.9 μm or less.

The use of this dielectric porcelain composition of the presentinvention enables the steady supply of a highly reliable and small highfrequency device.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a sectional view of a high frequency device using a dielectricporcelain composition in accordance with a preferred embodiment of thepresent invention.

FIG. 2 is a sectional view the high frequency device using thedielectric porcelain composition in accordance with the preferredembodiment of the present invention.

FIG. 3 is a sectional view of around an electrode end of the highfrequency device using the dielectric porcelain composition inaccordance with the preferred embodiment of the present invention.

FIG. 4 is a magnified view illustrating a surface of sintered dielectricporcelain composition in accordance with the preferred embodiment of thepresent invention.

REFERENCE MARKS IN THE DRAWINGS

-   1 Laminated body-   2 Internal electrode-   3 External electrode-   4 Space-   5 Columnar grain-   L Length from internal electrode end to dielectric porcelain body

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

One objective of the present invention is to achieve a dielectricporcelain composition whose relative permittivity is 30 or more, and ahigh frequency device using this dielectric porcelain composition.

The dielectric porcelain composition in a preferred embodiment of thepresent invention is described below. Characteristics of this dielectricporcelain composition are confirmed in accordance with the followingprocedures.

First, a first component powder forming the dielectric porcelaincomposition is described. As starting materials, BaCO₃, Nd₂O₃, TiO₂, andBi₂O₃, which are chemically highly pure (99 wt % or more), are used.After compensating their purity, they are weighed to achievepredetermined values for x, y, z, and w, respectively, in a compositionof xBaO—yNd₂O₃-zTiO₂-wBi₂O₃ (provided that x, y, z, and w are molarratios and x+y+z+w=100). These powdered materials and deionized waterare mixed in a ball mill for 17 hours. After mixing, a slurry is dried,placed in an alumina crucible, and provisionally fired at 1000° C. to1300° C. for two hours. After crushing the provisionally fired body, itis ground for 17 hours in the aforementioned ball mill and dried tocomplete the first component powder.

Next, preparation of a powder used as the second component is described.Starting materials are typically SiO₂, H₃BO₃, Al(OH)₃, BaCO₃, CaCO₃,SrCO₃, La₂O₃, Li₂CO₃, and ZnO. After compensating the purity of eachmaterial, the materials are weighed to achieve a predeterminedcomposition. Powders of these materials are mixed using a V blender witha V-shaped mixing container. After mixing, the mixture is placed in aplatinum or platinum-rhodium crucible, melted at between 1400° C. and1600° C., and quickly cooled down using a twin roller to create glasscullet. This cullet is ground in a ball mill for eight hours and driedto complete the second component powder. Table 1 shows constituents ofthe mixed second component.

TABLE 1 Compo- Constituents of the second component sition BaO SiO₂La₂O₃ Al₂O₃ B₂O₃ SrO CaCO₃ Li₂O ZnO A 34 45 10 5 5 1 B 32 41 16 5 5 1 C36 44 6 5 8 1 D 40 12 4 34 10 E 32 34 9 5 5 1 14 F 36 39 10 6 5 1 3

Powders of the first component, second component, and third componentare weighed in accordance with the compounding ratios shown in Tables 2Aand 2B. As shown in Tables 2A and 2B, a powder of the third component isone of powder of CuO, B₂O₃, GeO₂, Li₂O, and ZnO, or a mixture of one ofthese powders and ZnO. However, the third component is not limited tooxides. Other salts such as carbonates and nitrates may also be added.For example, Li₂CO₃ is applicable.

TABLE 2A Characteristics Compounding Compounding ratio Average FiringDeflec- Reac- Speci- Constituents of ratio of of 3^(rd) componentparticle Tempera- Qf tive tivity men 1st component 2^(nd) componentConstit- Constit- diameter/ ture/ Holding product/ Strength/ with No. xv z w Type Wt % uents Wt % uents Wt % μm ° C. time/hr εr GH MPa Ag  1*15 15 67 3 A 0 — — — — 0.72 Not — — — — — sintered  2* 15 15 67 3 A 5 —— — — 0.75 Not — — — — — sintered  3* 15 15 67 3 A 5 CuO 1.5 — — 0.75Not — — — — — sintered  4* 15 15 67 3 A 10 — — — — 0.76 Not — — — — —sintered  5* 15 15 67 3 A 10 CuO 1.5 — — 0.72 940 5 66 2690 Not Xmeasured  6* 15 15 67 3 A 15 CuO 1.5 — — 0.79 920 5 55 2200 Not Xmeasured  7* 15 15 67 3 A 20 — — — — 0.75 Not — — — — — sintered  8* 1515 67 3 A 20 CuO 1.5 — — 0.77 920 5 45 1900 Not X measured  9* 15 15 673 A 20 B₂O₃ 1.5 — — 0.74 940 5 42 1440 Not Δ measured 10* 15 15 67 3 A20 GeO₂ 1.5 — — 0.78 940 5 44 1520 Not Δ measured 11* 15 15 67 3 A 20Li₂O 1.5 — — 0.76 920 5 47 1170 Not ◯ measured 12* 15 15 67 3 A 20 ZnO1.5 — — 0.71 940 5 47 1930 Not Δ measured 13* 15 15 67 3 A 15 ZnO 1.5 —— 0.54 900 5 56 2520 170 Δ 14* 15 15 67 3 A 20 Li₂O 0.1 — — 0.85 Not — —— — — sintered 15* 15 15 67 3 A 20 Li₂O 0.25 — — 0.84 Not — — — — —sintered 16* 15 15 67 3 A 20 Li₂O 0.5 — — 0.80 920 5 49 1240 Not ◯measured 17* 15 15 67 3 A 20 Li₂O 0.1 ZnO 1.0 0.77 Not — — — — —sintered 18 15 15 67 3 A 10 Li₂O 0.1 ZnO 5.0 0.74 940 5 63 3380 170 ◯19* 15 15 67 3 A 15 Li₂O 0.25 ZnO 1.0 0.74 Not — — — — — sintered 20* 1515 67 3 A 15 Li₂O 0.25 ZnO 2.0 0.78 940 5 53 1710 Not ◯ measured 21 1515 67 3 A 15 Li₂O 0.25 ZnO 3.0 0.76 920 5 53 2160 160 ◯ 22 15 15 67 3 A15 Li₂O 0.25 ZnO 4.0 0.78 920 5 52 2620 160 ◯ 23 15 15 67 3 A 15 Li₂O0.25 ZnO 5.0 0.75 920 5 52 3170 170 ◯ 24 15 15 67 3 A 15 Li₂O 0.25 ZnO9.0 0.75 920 5 47 3000 170 ◯ 25 15 15 67 3 A 15 Li₂O 0.25 ZnO 5.0 0.59900 2 56 2950 170 ◯ 26 15 15 67 3 A 20 Li₂O 0.25 ZnO 3.0 0.74 920 5 442260 155 ◯ Specimen numbers marked * are comparison data. Reactivitywith Ag ◯: No reaction, Δ Partial reaction X Loss

TABLE 2B Characteristics Compounding Compounding ratio Average FiringDeflec- Reac- Spec- Constituents of ratio of of 3^(rd) componentparticle Tempera- Qf tive tivity imen 1st component 2^(nd) componentConstit- Constit- diameter/ ture/ Holding product/ Strength/ with No. xy z w Type Wt % uents Wt % uents Wt % μm ° C. time/hr εr GHz MPa Ag 2715 15 67 3 A 20 Li₂O 0.25 ZnO 4.0 0.72 920 5 44 2770 160 ◯ 28 15 15 67 3A 20 Li₂O 0.25 ZnO 5.0 0.73 920 5 44 2930 160 ◯ 29* 15 15 67 3 A 20 Li₂O0.25 ZnO 5.0 1.10 Not — — — — — sin- tered 30* 15 15 67 3 A 15 Li₂O 0.25ZnO 12.0 0.74 950 5 46 3000 160 ◯ 31* 15 15 67 3 B 20 CuO 1.5 — — 0.78940 5 56 1610 Not X meas- ured 32* 15 15 67 3 C 20 Li₂O 0.25 ZnO 5.00.77 940 5 53 2760 Not Δ meas- ured 33* 15 15 67 3 D 20 CuO 1.5 — — 0.75950 5 41 790 Not Not meas- meas- ured ured 34 15 15 67 3 E 15 Li₂O 0.25ZnO 5.0 0.72 900 5 50 2800 170 ◯ 35 15 15 67 3 F 15 Li₂O 0.25 ZnO 5.00.75 900 5 46 2200 160 ◯ 36 12 18 67 3 A 15 Li₂O 0.25 ZnO 5.0 0.72 940 546 2710 160 ◯ 37 16 12 69 3 A 15 Li₂O 0.25 ZnO 5.0 0.78 940 5 45 2820160 ◯ 38 16 16 65 3 A 15 Li₂O 0.25 ZnO 5.0 0.71 940 5 47 2900 170 ◯ 3915 15 68 2 A 15 Li₂O 0.25 ZnO 5.0 0.80 940 5 47 2950 170 ◯ 40 14 14 67 5A 15 Li₂O 0.25 ZnO 5.0 0.79 940 5 46 2830 170 ◯ 41* 14.5 14.5 63.5 7.5 A15 Li₂O 0.25 ZnO 5.0 0.80 900 — — — — — (melted) 42* 8 22 67 3 A 15 Li₂O0.25 ZnO 5.0 0.76 940 5 28 1800 Not Not meas- meas- ured ured 43* 22 867 3 A 15 Li₂O 0.25 ZnO 5.0 0.72 940 5 50 1600 Not Not meas- meas- uredured 44* 26 26 45 3 A 15 Li₂O 0.25 ZnO 5.0 0.78 940 5 69 1400 Not Notmeas- meas- ured ured 45* 8 8 81 3 A 15 Li₂O 0.25 ZnO 5.0 0.78 940 5 431900 Not Not meas- meas- ured ured 46* 15 15 67 3 A 0 Li₂O 0.25 ZnO 5.00.75 Not — — — — — sin- tered 47* 15 15 67 3 A 5 Li₂O 0.25 ZnO 5.0 0.75Not — — — — — sin- tered 48 15 15 67 3 A 10 Li₂O 0.25 ZnO 5.0 0.75 920 560 2900 170 ◯ 49 15 15 67 3 A 25 Li₂O 0.25 ZnO 5.0 0.75 900 5 39 2300165 ◯ 50 15 15 67 3 A 20 Li₂O 0.25 ZnO 5.0 0.86 920 5 45 3000 160 ◯ 5115 15 67 3 A 30 Li₂O 0.25 ZnO 5.0 0.76 920 5 33 2500 160 ◯ 52* 15 15 673 A 35 Li₂O 0.25 ZnO 5.0 0.75 950 5 25 2300 150 Δ Specimen numbersmarked * are comparison data. Reactivity with Ag ◯: No reaction, ΔPartial reaction X Loss

The first component, second component, and third component are mixed inthe ball mill by wet blending and ground. The average particle diameteris then measured using a laser diffraction particle size analyzer. Then,polyvinyl alcohol aqueous solution (5 wt % aqueous solution) is added at8 wt % to the ground powder as a binder. After mixing, the mixture isgranulated using a 32-mesh sieve. The sieved mixture is pressed into acylindrical shape 13 mm in diameter and about 7 mm thick under apressure of 100 MPa. The pressed body is heated at 600° C. for two hoursto burn out the binder, then fired at a temperature ranging from 900 to960° C. on a mullite setter for two to five hours. The dielectriccharacteristic for microwaves of the sintered body fired at atemperature that achieves the highest density is then measured. Theresonance frequency and Q value are calculated using the dielectricresonator method. Then, relative permittivity (εr) is calculated basedon the dimensions of the sintered body and the resonance frequency.Here, the resonance frequency is 3 to 7 GHz. The mechanical strength ofthe sintered body is measured according to JIS-R1601. Tables 2A and 2Bshow the measurement results. The Qf product in Tables 2A and 2B is aproduct of the Q value and frequency f used for measurement. Theresonance frequency f is between 3 and 7 GHz, and varies depending onthe size and shape of the specimen. Therefore, the Qf product, which isnot affected by the size or shape of the specimen, is calculated forcomparison. This is a general method used in the industry.

Next, a ceramic slurry is prepared by mixing and dispersing an organicbinder, plasticizer, and organic solvent in the mixed powder of thefirst, second and third components. This ceramic slurry is applied to abase film such as a PET film, using a doctor blade method or die-coatingmethod, to prepare a ceramic green sheet.

Ag paste is then screen-printed on the ceramic green sheet, forming aline 200 to 500 μm wide on a surface or inner layer of the laminatedbody to complete a laminated body about 1 mm thick. This laminated bodyis fired at a range of temperatures between 900° C. and 940° C. toconfirm reactivity with Ag.

The first component is represented by Formula (1).

XBaO—yNd₂O₃-zTiO₂-wBi₂O₃   (1),

-   -   whereas x, y, z, and w are molar ratios, and x+y+z+w=100.

These x, y, z, and w values are preferably within the range shown in thefollowing Formulae (2) to (5), respectively.

12≦x≦16   (2)

12≦y≦16   (3)

65≦z≦69   (4)

2≦w≦≦5   (5)

As shown in specimen Nos. 41 to 45 in Table 2B, relative permittivitybecomes 30 or smaller in some cases, or the Qf product becomes lowerthan 2000 GHz, when the second component is glass composition A, andwhen x, y, z, and w are not in the ranges shown by Formulae (2) to (5).In addition, the specimens do not sinter as porcelain in some cases. Forthe above reasons, such composition is not preferable as the dielectricporcelain composition.

When the second component contains 12 wt % or more of La₂O₃ shown inTable 1, such as specimen No. 31 using glass composition B, sinteringperformance degrades, and the Qf product also reduces. Accordingly, suchcomposition is not preferable as the dielectric porcelain composition.

When the second component contains 8 wt % or less of La₂O₃ shown inTable 1, such as specimen No. 32 using glass composition C, loss of Agis noticed due to partial reaction of Ag with porcelain. When acompounding ratio of B₂O₃ becomes 7 wt % or more, gelation occurs bymixing and dispersing composition, in which mixed powder, organicbinder, and plasticizer are dispersed in an organic solvent.

When gelation occurs, a sheet with stable film thickness and densitycannot be manufactured in a subsequent sheet-forming process.

When the second component contains no La₂O₃ shown in Table 1, such asspecimen No. 33 using glass composition D, sintering performance is notsufficient even at 950° C., and the Qf product further reduces.

On the other hand, in case of specimen Nos. 34 and 35, which usescompositions E and F containing ZnO or Li₂O in glass, a softening pointof glass can be lowered, improving the sintering performance ofdielectric porcelain composition.

In the case of specimen Nos. 1 to 3 in which a compounding ratio of thesecond component is less than 10 wt %, or specimen Nos. 4 and 7 in whichno third component is added, these specimens do not sinter even at 940°C., which does not fit to the objective of the present invention. Alsoeven when Li₂O or ZnO is added as the third component, it becomesdifficult to ensure sintering when the compounding ratio of the secondcomponent is less than 10 wt %, which is the case of specimen Nos. 46and 47. In the case of specimen No. 52, in which the second component isadded over 30 wt %, the sintering temperature increases in addition topermittivity becoming lower than 30. Reaction with Ag also acceleratesby increased addition of glass. Accordingly, such compositions are notpreferable.

In the case of specimen Nos. 5, 6, and 8 which uses CuO as the thirdcomponent, the firing temperature can be reduced. However, reactivitywith Ag is extremely high, causing disappearance of the Ag-paste lineformed on the surface or inner layer. Accordingly, such composition isnot preferable for forming the device.

In the case of using only B₂O₃, GeO₂, or ZnO as the third component, asin the case of specimen Nos. 9, 10, 12, and 13, sintering temperature isnot as low as the cases using CuO. The Qf product is also lower than2000 GHz, which is not preferable.

In the case of using only Li₂O as the third component, as in the case ofspecimen No. 11, low-temperature sintering at 920° C., same as thatusing CuO, is feasible. However, the Qf product is extremely low around1000 GHz. In addition, in this case, gelation occurred at making slurryby adding a binder, plasticizer, and solvent to the powder specimen.Accordingly, steady sheet-forming is not feasible.

When a laminated sintered body shown in FIG. 1 is prepared using amaterial composition of specimen No. 11, and its terminal electrode isplated, the strength of the terminal electrode degrades significantly.One cause is assumed to be elution of Li component into platingsolution. Accordingly, addition of Li₂O is preferably as small aspossible for securing sintering performance.

Specimen Nos. 14 to 16 achieve low-temperature sintering by the use ofLi₂O, but an additive amount of Li₂O is reduced to reduce an effect onthe Qf product. However, sintering is not feasible when 0.1 wt % or 0.25wt % is added, and thus 0.5 wt % is needed. However, even when 0.5 wt %is added, the Qf product is not so different from that of specimen No.11 to which 1.5 wt % is added. Accordingly, no significant improvementis noticed.

Then, in addition to Li₂O, improvement is attempted by adding ZnO whichdemonstrates the highest Qf product in the third component used inspecimen Nos. 8 to 12. As a result, sintering performance is secured andhigher Qf product is achieved by adding 3 to 10 wt % of ZnO when a glassadditive amount of the second component is within the range of thepresent invention, as shown in specimen Nos. 17 to 28.

However, sintering performance is not secured in specimen Nos. 17 and 19and the Qf product is low in specimen No. 20, to which ZnO is added lessthan 3.

Table 3 shows the relation of constituents of dielectric porcelaincomposition, slurry viscosity, and the strength of terminal electrodeafter firing.

TABLE 3 Compounding Constituents of ratio of the Compounding ratio ofthe Average Slurry Terminal the first second third component particleviscosity electrode Specimen component component Com- Com- Wt diameterPa's strength No. x y z w Type Wt % position Wt % position % μm (1/s)N/mm 11 * 15 15 67 3 A 20 Li₂O 1.5 — — 0.76 Gelation — 51 15 15 67 3 A20 Li₂O 0.1 ZnO 5.0 0.74 1~3 4 28 15 15 67 3 A 20 Li₂O 0.25 ZnO 5.0 0.731~3 4 52 15 15 67 3 A 20 Li₂O 0.4 ZnO 5.0 0.75 1~3 4 53 15 15 67 3 A 20Li₂O 0.6 ZnO 5.0 0.75 1~3 4 54 15 15 67 3 A 20 Li₂O 0.7 ZnO 5.0 0.75 5 355 15 15 67 3 A 20 Li₂O 1 ZnO 5.0 0.75 >10 1.5 56 * 15 15 67 3 A 20 Li₂O1.5 ZnO 5.0 0.75 Gelation —

As shown in Table 3, partial gelation occurs when preparing slurry, sameas in specimen No. 11, in specimen Nos. 54 to 56 if the additive amountof Li₂O exceeds 0.6 wt % in spite of Li₂O and ZnO being added as thethird component. This increases the viscosity of the slurry. Inparticular, specimen No. 56 is completely gelated. Accordingly, sheetforming is not absolutely impossible, but it is difficult to form sheetsreliably for mass production using specimen Nos. 54 and 55. When alaminated sintered body is prepared using these specimens and theterminal electrodes are plated, the strength of the terminal electrodesdegrades. From the above reasons, Li₂O is added at between 0.1 and 1.0parts by weight, and preferably between 0.1 and 0.6 wt %.

If ZnO is added at over 10 wt %, as in the case of specimen No. 30, thesintering performance significantly degrades, although there is noproblem with the characteristics of permittivity and Q value. In otherwords, specimen No. 30 needs to be heated at a high temperatureexceeding 950° C., which is not preferable, to obtain a dense sinteredbody.

If average particle diameter is 0.9 μm or smaller, such as in specimenNos. 28 and 50, sintering performance is secured. However, if thediameter is larger than 0.9 , μm, as in specimen No. 29, the compositiondoes not sinter.

On the other hand, if the average particle diameter is reduced to 0.6 μmor smaller by grinding, as in specimen No. 25, sintering at even lowertemperatures becomes feasible, and thus it is preferable since itpermits more rapid sintering. However, although sintering at 900° C. issecured even if only ZnO is added as the third component, as in specimenNo. 13, by making the particle diameter 0.6 μm or smaller as describedabove, the test reveals that a part of Ag and porcelain react, which isnot preferable. Specimen No. 25 contains Li₂O, and thus it can beassumed that the presence of Li₂O has the effect of suppressing thereaction between the Ba—Nd—Ti—Bi—O body and Ag.

Conditions for the dielectric porcelain composition of the presentinvention are described below.

(First condition) When the first component is represented by thefollowing general Formula (1), the aforementioned x, y, z, and w arewithin the ranges in Formulae (2) to (5), respectively.

XBaO—yNd₂O₃-zTiO₂-wBi₂O₃   (1)

Here, x, y, z, and w are molar ratios, and x+y+z+w=100.

12≦x≦16   (2)

12≦y≦16   (3)

65≦z≦69   (4)

2≦w≦5   (5)

(Second condition) The second component is a glass containing thefollowing compounds in the compounding ratios in parentheses. Morespecifically, these are BaO (30 to 37 wt %), SiO₂ (33 to 46 wt %), La₂O₃(8 to 12 wt %), Al₂O₃ (3 to 7 wt %), SrO (0 to 1 wt %), Li₂O (0 to 10 wt%), ZnO (0 to 20 wt %), and B₂O₃ (7 wt % max.).

(Third condition) When the sum of the first component and secondcomponent is 100, the compounding ratio of the second component isbetween 10 wt % and 30 wt %.

(Fourth condition) When the sum of the first component and secondcomponent is 100 parts by weight, the third component is 0.1 to 1 partsby weight of Li₂O and 3 to 10 parts by weight of ZnO.

(Fifth condition) Dielectric mixed powder forming the dielectricporcelain composition before firing has the average particle diameter of0.9 μm or smaller.

The dielectric porcelain compositions in specimen Nos. 18, 21 to 28, 34to 40, and 48 to 51 satisfy all the above first to fifth conditions, andthus the compositions in these specimens are included in the presentinvention. All these specimens can be sintered at 940° C. or lower, andshow good microwave dielectric characteristics including relativepermittivity (εr) of 30 or more and the Qf product of 2000 GHz orhigher. In addition, low reactivity with Ag is confirmed. Still more, amechanical strength is 155 Mpa or higher in all these specimens, whichis higher than 140 MPa, a deflective strength of conventionalBi₂O₃—CaO—Nb₂O₅ porcelain.

Table 4 shows the percentage of columnar grain on the surface of thesintered body, the long axis/short axis ratio of the columnar grain, thedeflective strength of the sintered body, and the reactivity of the Agelectrode and the body.

TABLE 4 Percentage of Long axis/short Deflective columnar axis ratio ofstrength Reactivity NO. grain % columnar grain MPa with Ag a <10 <15 170◯ b 30 <20 165 ∘ c 50 ≦25 160 ∘ d 60 ≦25 155 ∘ e* 75 >25 130 Δ

FIG. 4 illustrates the state of the surface of the sintered bodyobserved using a scanning electron microscope (SEM). An example ofcolumnar grain 5 can be observed in the area marked with a dotted linein FIG. 4. The deposition percentage of columnar grain and its longaxis/short axis ratio are controllable by changing conditions such asfiring conditions, starting particle diameter, and ground particlediameter.

As shown in No. e in Table 4, the deflective strength falls to 140 MPaor lower if the percentage of columnar grain exceeds 60% of the entiresurface. This reduces the advantage of mechanical strength compared tothat of Bi₂O₃—CaO—Nb₂O₅ porcelain, and also increases the trend forreactive loss of the electrode due to higher reactivity with the Agelectrode. Specimen numbers marked * in Tables 2A, 2B, 3, and 4 arespecimens for comparison. In Tables 2A, 2B, and 4, reactivity with Ag isindicated by O (no reaction), Δ (partial reaction), and X (electrodeloss due to reaction).

A larger long axis/short axis ratio of columnar grain, i.e., a so-calledlarger growth of columnar grain, reduces the deflective strength to 140MPa or lower, which is not preferable as the dielectric porcelaincomposition. In addition, if the long axis/short axis ratio rises,reactivity with Ag increases when the composition is simultaneouslyfired with Ag for manufacturing devices. This results in a greaterdegree of loss at the electrode end. Accordingly, this is also notpreferable, taking into account the need for firing in the presence ofAg.

As described above, the percentage of columnar grain is preferably 60%or lower relative to the entire surface, and the long axis/short axisratio of columnar grain is preferably between 1 and 25.

A high frequency device shown in FIGS. 1 and 2 is a laminated resonatorincluding inner-layer electrode 2 forming a high frequency circuitconfigured with a strip line and capacitor in the inner layer oflaminated body 1 made using the aforementioned dielectric porcelaincomposition. The dimensions of the high frequency device are, forexample, 8 mm long, 5 mm wide, and 0.9 mm high. This structuredemonstrates a high resonance characteristic.

FIG. 2 is a sectional view of a high frequency device using thedielectric composition in the preferred embodiment of the presentinvention. FIG. 3 is a magnified view of around the electrode end.

This device is characterized by its length L, between the internalelectrode end and dielectric porcelain body, being 15 μm or less. Thisspace 4 is a phenomenon often noticed in the internal electrodes oflaminated ceramics for reasons that include reaction between Ag and theceramic body and attraction of the electrode by firing shrinkage. Sincelength L is 15 μm or less, the electric field becomes concentrated onthe electrode end, and thus conductor loss is large at the end. Thisprevents degradation of the Q value of the resonator. The relationbetween length L, which shows the size of the space, and the Q value ofthe resonator is shown in Table 5.

TABLE 5 L (μm) Q value 0 135 5 132 10 130 15 128 20 105 30 96

As shown in Table 5, the Q value of the resonator remains almostconstant if the length L is 15 μm or less. On the other hand, if lengthL exceeds 15 μm, the Q value of resonator drops significantly, as shownin Table 5, due to the smaller electrode width, which is not preferable.

As described above, the dielectric porcelain composition can be sinteredat a temperature that allows simultaneous firing with Ag, has lowreactivity with Ag electrode; and has high relative permittivity, Qvalue and mechanical strength. A small high frequency device with highperformance and high mechanical strength can be offered by using thisdielectric porcelain composition for the laminated body forming the highfrequency device shown in FIG. 1.

INDUSTRIAL APPLICABILITY

The dielectric porcelain composition of the present invention can besintered at a low temperature of around 900° C., has low reactivity withAg, and high relative permittivity and Q value. In addition, a slurrycan be reliably prepared. The dielectric porcelain composition alsoshows high plating resistance. The high frequency device used in a highfrequency range can thus be offered by employing the dielectricporcelain composition of the present invention.

1. A dielectric porcelain composition comprising: a first componentrepresented by a formula of xBaO—yNd₂O₃-zTiO₂-wBi₂O₃; x, y, z, and wsatisfying 12≦x≦16, 12≦y≦16, 65≦z≦69, and 2≦w≦5, provided that x, y, z,and w are molar ratios and x+y+z+w=100; a second component including, inweight ratio, 30 to 37 wt % of BaO, 33 to 46 wt % of SiO₂, 8 to 12 wt %of La₂O₃, 3 to 7 wt % of Al₂O₃, 0 to 1 wt % of SrO, 0 to 10 wt % ofLi₂O, 0 to 20 wt % of ZnO, and 7 wt % or less of B₂O₃, a compoundingratio of the second component being 10 wt % to 30 wt % when a sum of thefirst component and the second component is 100; and a third componentincluding 0.1 to 1 parts by weight of Li₂O and 3 to 10 parts by weightof ZnO, relative to 100 parts by weight of the sum of the firstcomponent and the second component; wherein an average particle diameterof a dielectric mixed powder before firing is not greater than 0.9 μm,the dielectric mixed powder including the first component powder, thesecond component powder, and the third component powder; and thedielectric porcelain composition is a sintered body made by firing thedielectric mixed powder.
 2. The dielectric porcelain composition ofclaim 1, wherein the sintered body has a columnar grain on a part of itssurface, and a percentage of the columnar grain is not greater than 60%of an entire surface.
 3. The dielectric porcelain composition of claim2, wherein the sintered body has the columnar grain in a part of a finestructure of its surface, and a ratio of a long axis to a short axis ofthe columnar grain is 1≦(Long axis/short axis)≦25.
 4. A high frequencydevice comprising: a laminated body including a dielectric porcelaincomposition; and an internal electrode forming a predetermined highfrequency circuit in an inner layer of the laminated body; wherein thedielectric porcelain composition includes a first component, a secondcomponent, and a third component, the first component being representedby a formula of xBaO—yNd₂O₃-zTiO₂-wBi₂O₃; x, y, z, and w satisfying12≦x≦16, 12≦y≦16, 65≦z≦69, and 2≦w≦5, provided that x, y, z, and w aremolar ratios and x+y+z+w=100; the second component including, in weightratio, 30 to 37 wt % of BaO, 33 to 46 Wt % of SiO₂, 8 to 12 wt % ofLa₂O₃, 3 to 7 wt % of Al₂O₃, 0 to 1 wt % of SrO, 0 to 10 wt % of Li₂O, 0to 20 wt % of ZnO, and 7 wt % or less of B₂O₃, a compounding ratio ofthe second component being 10 wt % to 30 wt % when a sum of the firstcomponent and the second component is 100; and the third componentincluding 0.1 to 1 parts by weight of Li₂O and 3 to 10 parts by weightof ZnO, relative to 100 parts by weight of a sum of the first componentand the second component; wherein an average particle diameter of adielectric mixed powder before firing is not greater than 0.9 μm, thedielectric mixed powder including the first component powder, the secondcomponent powder, and the third component powder; and the dielectricporcelain composition is a sintered body made by firing the dielectricmixed powder.
 5. The high frequency device of claim 4, wherein thesintered body has a columnar grain on a part of its surface, and apercentage of the columnar grain is not greater than 60% of an entiresurface.
 6. The high frequency device of claim 5, wherein the sinteredbody has the columnar grain in a part of a fine structure of itssurface, and a ratio of a long axis to a short axis of the columnargrain is 1≦(Long axis/short axis)≦25.
 7. The high frequency device ofclaim 4, the high frequency device comprising: the laminated body madeof the dielectric porcelain composition; and the internal electrodeforming the predetermined high frequency circuit in the inner layer ofthe laminated body; wherein the high frequency device has a spacebetween an end of the internal electrode and a body of the dielectricporcelain, a length of the space being not longer than 15 μm.
 8. Adielectric porcelain composition made of a sintered body, the sinteredbody comprising: a first component being represented by a formula ofxBaO—yNd₂O₃-zTiO₂-wBi₂O₃; x, y, z, and w satisfying 12≦x≦16, 12≦y≦16,65≦z≦69, and 2≦w≦5, provided that x, y, z, and w are molar ratios andx+y+z+w=100; a second component including, in weight comparison, 30 to37 wt % of BaO, 33 to 46 wt % of SiO₂, 8 to 12 wt % of La₂O₃, 3 to 7 wt% of Al₂O₃, 0 to 1 wt % of SrO, 0 to 10 wt % of Li₂O, 0 to 20 wt % ofZnO, and 7 wt % or less of B₂O₃, a compounding ratio of the secondcomponent being 10 wt % to 30 wt % when a sum of the first component andthe second component is 100; and a third component including 0.1 to 1parts by weight of Li₂O and 3 to 10 parts by weight of ZnO, relative to100 parts by weight of a sum of the first component and the secondcomponent; wherein the sintered body has a columnar grain on a part ofits surface, and a percentage of the columnar grain is not greater than60% of an entire surface.
 9. The dielectric porcelain composition ofclaim 8, wherein the sintered body has the columnar grain in a part of afine structure of its surface, and a ratio of a long axis to a shortaxis of the columnar grain is 1≦(Long axis/short axis≦25.
 10. The highfrequency device of claim 5, the high frequency device comprising: thelaminated body made of the dielectric porcelain composition; and theinternal electrode forming the predetermined high frequency circuit inthe inner layer of the laminated body; wherein the high frequency devicehas a space between an end of the internal electrode and a body of thedielectric porcelain, a length of the space being not longer than 15 μm.11. The high frequency device of claim 6, the high frequency devicecomprising: the laminated body made of the dielectric porcelaincomposition; and the internal electrode forming the predetermined highfrequency circuit in the inner layer of the laminated body; wherein thehigh frequency device has a space between an end of the internalelectrode and a body of the dielectric porcelain, a length of the spacebeing not longer than 15 μm.